1. Field of the Invention
The present invention relates to a casting nozzle and its producing method, such as an immersion nozzle or shroud having blowout holes to prevent clogging with nonmetallic impurities and also with a method for producing the same.
2. Description of the Prior Art
In the continuous casting of molten metal (like molten steel), an immersion casting nozzle designed to blow an inert gas, during casting, into the molten metal through a cylindrical part of the nozzle has come into general use recently. The blowing of an inert gas is intended to prevent clogging of the nozzle with nonmetallic impurities such as alumina sticking to the wall of the pouring hole.
An example of the immersion nozzle is disclosed in Japanese Patent Laid-open No. 56-102357. It has such a structure that a hollow chamber having an annular section is formed in the axial direction of the nozzle. A gas is blown out through this hollow chamber into the molten metal flowing through the nozzle. The gas flow prevents nonmetallic impurities such as alumina from sticking to the inside wall of the immersion nozzle.
However, in this type of nozzle, the effect of gas blowing for preventing the sticking is not satisfactory. Sticking of nonmetallic impurities to the outlet of the nozzle makes the casting nozzle of limited repeated use for continuous casting.